The present invention relates to a manufacturing method for a device which manufactures a device by transferring elements, a device manufactured by the method, an electro-optic device, and electronic equipment.
Recently, for electro-optic devices such as liquid crystal electro-optic devices, active matrix type devices which use thin film elements such as thin film transistors (hereunder, TFT), thin film diodes (hereunder, TFD) or the like, have become the mainstream. However, regarding the conventional electro-optic devices furnished with amorphous silicon TFT or polycrystalline silicon TFT, manufacturing cost per unit area is expensive. Hence, in the case where large electro-optic devices are to be manufactured, a problem is that the cost becomes very expensive. One cause for this is the effective area utilization ratio of the transistor circuit on the substrate of the liquid crystal electro-optic device is low, and wastage of the thin film element constituent material which forms the film is considerable. That is to say, in the case where amorphous silicon TFT or polycrystalline silicon TFT are to be formed on the substrate by the conventional techniques, after film-forming the amorphous silicon on one side by CVD or the like, the unnecessary parts are removed by etching. However, the TFT circuit area inside the pixel area is only from a few % to several 10% and the thin film element constituent material which is film-formed on the rest of pixel electrode part is discarded by etching. In cases where it is possible to effectively manufacture only the TFT circuit section on the substrate, it is possible to greatly reduce the cost, especially of large electro-optic devices. Therefore various techniques have been studied.
Conventionally, as a technique for arranging an LSI circuit which is manufactured on a silicon wafer, onto another substrate, a so called microstructure method developed by Alien Technology Co. is well known (for example, refer to the Information DISPLAY, Vol. 15, No. 11 (November 1999)).
The microstructure technique is characterized in that it involves separating LSI circuits manufactured on a silicon wafer into microchips (=microstructures), and then pouring solvent dispersed with the microstructures onto a substrate previously patterned with holes for filling, so that the microstructures are arranged at predetermined positions on the substrate. According to this microstructure technique, microstructures which are formed in a large number on a silicon wafer can be dispersingly arranged on a substrate. Moreover, since this gives a discrete type arrangement where unit elements are separated on the substrate, the ability to follow the curvature and bending of the substrate is excellent, so that it is applicable to flexible substrates.
However, in the microstructure technique, there is the problem in that reliable arrangement of the microstructures on the substrate and accurate positioning are difficult. Moreover, since the directions in which the microstructures are arranged are random, special circuits to cope with this must be provided for the microstructures, with the problem of incurring a cost increase. In the present state, this problem is avoided by designing the circuits on microstructures in four-way symmetry.
Further, in the manufacture of color filters of liquid crystal displays, a method called an LITI process is well known, in which; a donor sheet formed by the sequential lamination of respective layers of; substrate/adhesion layer/optical absorption layer/protective layer/colored film layer/thermal melting adhesion layer, is superposed on an original substrate; the optical absorption layer is then photoirradiated for a partial area of the donor sheet; heat generated here melts and adheres the thermal melting adhesion layer; and as a result only the photoirradiated area is transferred onto the substrate (for example, refer to the U.S. Pat. No. 6,057,067).
However, this conventional technique is used for manufacturing color filters or the like for liquid crystal display elements, and other application possibilities have not been specified.
Furthermore, as a method for transferring a thin film element such as a TFT or the like formed on a substrate, to a transfer body, the present applicant has developed and applied to patent, a transferring method for a thin film element, which is characterized in having; a process for forming a separation layer on a substrate of high reliability and which can transmit laser light; a process for forming a transfer layer containing a thin film element on the separation layer; a process for adhering the transfer layer containing the thin film element to the transfer body via an adhesion layer; a process for photoirradiating the separation layer and generating exfoliation in the layer and/or on interface of the separation layer; and a process for separating the substrate from the separation layer (refer to the Japanese Patent Application No. Hei 10-125931).
Likewise, the present applicant has developed and applied to patent a method for transferring a thin film element, which is characterized in having: a first process for forming a first separation layer on a substrate; a second process for forming a transfer layer containing a thin film device on the first separation layer; a third process for forming a second separation layer on the transfer layer; a fourth process for adhering a primary transfer body on the second separation layer, a fifth process for removing the substrate from the transfer layer with the first separation layer made a border, a sixth process for adhering a secondary transfer body on the undersurface of the transfer layer, and a seventh process for removing the primary transfer body from the transfer layer with the second separation layer made a border; and the transfer layer containing the thin film device is transferred to the secondary transfer body (refer to the Japanese Patent Application No. Hei 11-26733).
According to these transferring techniques, it is possible to transfer a detailed and high performance functional device onto a desired substrate.
However, the conventional transfer techniques have the following problems.
That is to say, since the conventional transfer techniques are to transfer all of the thin film elements such as TFTs which are formed on the substrate onto the final substrate, then as with an active matrix substrate for electro-optic devices, a large number of TFTs are required. However, in order to manufacture a substrate for which the arranged area of the TFTs is small with respect to the whole substrate area, it is necessary to specially manufacture a substrate where a large number of TFTs are formed at the same intervals as for the final substrate, and transfer these to the final substrate, or it is necessary to repeat the transfer many times, which does not always give a reduction in cost.
Further, since the conventional transfer techniques are to transfer all the thin film elements such as TFTs which are formed on the substrate onto the final substrate, then the larger the area of the substrate, the higher the characteristic required for the irradiating laser light, that is, the higher the power and uniformity, so that it becomes difficult to obtain a laser light source which satisfies the required performance, and large sized highly accurate irradiation equipment becomes necessary for the laser light irradiation. In addition, when irradiating a high power laser light, the thin film elements may be heated above their heat resistant critical temperature, so that the function of the thin film element itself may be lost. Hence, there is the problem that the transfer process itself becomes difficult.
Furthermore, similarly to the conventional transfer techniques, in the case where the thin film elements formed on the substrate are transferred for each device, for example, an insulating film is continuously formed over the whole surface of the thin film element. Therefore cracking may occur when the final substrate is bent after the transfer, and the ability to follow the bending of the substrate is not good. As a result, in the conventional transfer techniques, the degree of freedom for selecting the final substrate is limited.